Traditional paint spray systems, of the type employed in car manufacturing, may consist of several (say 30) separate paint lines, each providing a different coloured paint to the spray booth. In general, only one colour is sprayed at any one time so only one line is actively employed at any instance. However, even when not being sprayed, it is necessary to circulate the paint in each line through the system at a minimum velocity to prevent the pigments from separating from the carrier fluid.
To ensure that the paint is at the required pressure for spraying, a BPR is used in combination with the paint pump to regulate and maintain the required fluid back pressure at the spray booth. In traditional systems, the BPR is adjusted manually and uses a coil spring, which is used to maintain the paint pressure upstream of the regulator by controlling the fluid flow rate. Also, in many systems (such as those employing certain types of turbine or lobe pumps) the pump will be set to operate at a fixed pressure and flow rate and the BPR used to maintain the set pressure. In this type of system, the BPR controls system pressure by adjusting flow rate to compensate for variations in the amount of fluid used at the paint ‘take offs’. Thus, each line is usually operated at the flow conditions required for spraying, whether the paint is being used or merely circulated. This is extremely inefficient and results in a large waste of energy. For example, a system operating 24 hours a day may only be required to spray each individual colour for, say, 1 hour a day. Each pump would be operated at the pressure and flow rate required to meet the system requirement for 24 hours a day even though the paint is only required to operate at that pressure for 1 hour a day.
In addition, a pump that is required to operate at a higher speed and pressure for a longer period of time is likely to require maintenance in a much shorter period of time than one that is used more conservatively.
It is an object of the present invention to provide an improved BPR for use in a paint circulation system, which alleviates the aforementioned problems.